Solid-liquid separation slurry

Mydlarz, I. and Jones, A.G., 1989. Crystallization and subsequent solid-liquid separation of potassium sulphate. Part II Slurry filtrability. Chemical Engineering Research and Design, 67, 294-300. 

The method for the recovery of tantalum and niobium was developed for use on secondary raw materials in the form of oil-contaminated sludge. Uchino and Azuma [486] suggested using solid-liquid separation of oil from the slurry prior to the recovery of tantalum and niobium from the raw material. 

The solid-liquid separation of shinies containing particles below 10 pm is difficult by conventional filtration techniques. A conventional approach would be to use a slurry thickener in which the formation of a filter cake is restricted and the product is discharged continuously as concentrated slurry. Such filters use filter cloths as the filtration medium and are limited to concentrating particles above 5 xm in size. Dead end membrane microfiltration, in which the particle-containing fluid is pumped directly through a polymeric membrane, is used for the industrial clarification and sterilisation of liquids. Such process allows the removal of particles down to 0.1 xm or less, but is only suitable for feeds containing very low concentrations of particles as otherwise the membrane becomes too rapidly clogged.2,4,8... 

The solids-liquid separation of slurries containing particles below 10 xm is difficult by conventional filtration techniques. A conventional approach would be to use a slurry thickener in which the formation of a filter cake is restricted and the product is discharged continuously as a concentrated slurry. Such filters use filter cloths as the filtration medium... 

Many industrial processes begin with a leaching step, yielding a slurry that must be clarified before solvent extraction. The solid-liquid separation is a costly step. The solvent extraction of unclarified liquids ( solvent-in-pulp ) has been proposed to eliminate solid-liquid separation. The increased revenue and reduced energy cost make this an attractive process, but many problems remain to be solved loss of metals and extractants to the solid phase, optimization of equipment design, effluent disposal, etc. 

The nature and sizing of equipment depends on the economic values and proportions of the phases as well as certain physical properties that influence relative movements of liquids and particles. Pressure often is the main operating variable so its effect on physical properties should be known. Table 11.1 is a broad classification of mechanical processes of solid-liquid separation. Clarification is the removal of small contents of worthless solids from a valuable liquid. Filtration is applied to the recovery of valuable solids from slurries. Expression is the removal of relatively small contents of liquids from compressible sludges by mechanical means. 

Homo- and copolymers of DADMAC are widely used for solid/liquid separations (dewatering) of different slurries in the mining industry. Specific examples of the minerals treated with these polymers include coal, taconite, trona, sand,... 

Although the slurry reactor offers advantages in terms of efficient heat removal and temperature homogeneity, an efficient solid-liquid separation step is required to recover the product. The catalyst needs to be highly mechanically stable to offer sufficient resistance against attrition. 

An example of a solid-liquid phase separation - often referred to as a mechanical separation - is filtration. Filters are also used in gas-solid separation. Filtration may be used to recover liquid or solid or both. Also, it can be used in waste-treatment processes. Walas [6] describes many solid-liquid separators, but we will only consider the rotary-drum filter. Reliable sizing of rotary-drum filters requires bench and pilot-scale testing with the slurry. Nevertheless, a model of the filtering process will show some of the physical factors that influence filtration and will give a preliminary estimate of the filter size in those cases where data are available. 

FIG. 18 146 Coding the settling characteristics of a slurry. Purchas, Solid/Liquid Separation Equipment Scale-Up, Uplands Press, Croydon, England, 1977, p. 11, by permission.)... 

Cell recycle fermentors consist of two main units a vessel where the biomass is allowed to grow, and a membrane separation unit (as in Figure 7.40). Vessels are usually designed to insure a uniform concentration of nutrients and pH throughout the whole volume. Due to complete mixing, process control and stability of the microbial slurry are not difficult to achieve.88 After anaerobic stabilization, when the biomass is well developed, the reactor biomass is pumped to the UF unit where solid-liquid separation occurs. The sludge is flushed back to the reactor. In most cases, the flow rate of nutrient feed is kept equal to the permeate flow rate thus keeping a constant liquid level in the anaerobic reactor. 

Level. Level control using a control valve to throttle the exit flow rate presents a potential for plugging at the constricting point. Attrition of the crystals from the shear in the valve will generate additional nuclei, especially if the crystallizer head is insufficient to supply slurry to the downstream process and a centrifugal pump is required upstream of the valve. If the slurry is sent to solid-liquid separation equipment, the nuclei are inconsequential because they... 

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